Magnetron generator



Sept. 13, 1938. I K. FRITZ 2,130,002

MAGNETRON GENERATOR Filed Dec. 51, 1935 INVENTOR. KA L FRITZ 'ATTORNEY.

Patented Sept. 13, 1938 MAGNETRQN GENERATOR Karl Fritz, Berlin, Germany,assignor to Telefunken Gesellschaft fiir Drahtlose Telegraphic m. b. H3.Berlin, Germany, a corporation of Germany Application December 31, 1935,Serial No. 56,856- In Germany December 22, 1934 6 Claims. (01.. 250-36)The present invention relates to magnetron Figs. 7 and 8 showrespectively two different generators, and the methods of controllingthe embodiments of my invention. frequency thereof. It is among theobjects of In Fig. 1 the vector H represents the main my invention toprovide means in a magnetron component of the magnetic field extendingin the discharge tube circuit such that high frequency direction of theanode axis. Item Q is the vector 5- oscillations may be controlled froman outside of an auxiliary high frequency field for instance source, ifdesired, and such that these oscillations at a right angle to H. Item Fis the effective may be multiplied in an output circuit from said fieldvector resulting from the two components 1 discharge tube. and formingan angle a with the normal principal 10 It has been proposed separatelyto control by field H whereby the value of this angle depends means ofhigh frequency the voltage of magneupon the value of the cross field Q.The manner trons; furthermore it has been suggested to carry and reasonfor the angle a effecting a determining out the control by means of acircular high freinfluence upon the oscillation performance will quencymagnetic field (high frequency current now be described. I

control). As an example a magnetron will be considered In the methodaccording to the invention there having cylindrically arranged platesegments and is utilized as separate control the relationship bea singlecathode in the axis of the anode cylinder.

tween the plate current Ie and the angle or; be-- The principal magneticfield may extend approxitween the resultant magnetic field and the axismately parallel to this axis. With a symmetrical of the electrodesystem. There is hereby constructure and suitably chosen electrical andmagsidered on the one hand the magnitude of the netic operatingconditions it will be found that plate current and on the other hand,the current there is a dependence of the total emission currentdistribution on the plate segments. Two difierent upon the angl asrepresented y Curves in F g. modes of construction will be obtained buthav- In the working poin X Q= on this ing common characteristicfeatures, namely the curve the electron courses are level and most of25' separate control by utilizing the aforementioned t t o s a e jusprevented m e c i angle relations. The magnitude of the plate curtanode- I-Ience the falling off of the plate rent depends in a highdegree upon the value of Cur ent. this angle. The method according tothe inven- In maintaining a working point Y and Y retion possessesvarious advantages. In the first p e y, a greater number of electronsarrives 30 place, the control energy is extremely low, and at theanodes. This can be explained as follows:- secondly the method isparticularly well suited for There pp 110W besides the normalPrincifrequency doubling and frequency multiplication. D fi d H, a C sfield Causing the resultant The idea underlying the present inventionrefield F to form a finite angle 0: with the axis of sides in effectingthe separate control of the electhe anode cylindere e o s o longer tronsby controlling their direction offlight. In v i pl at ri ht an les to hcathode, order to do this the principal magnetic field of a, but windthemselves in a screw-like fashion about magnetron is operated in one ofthe ordinary the turned resultant magnetic field as axis and circuitsand is superposed by a weak high frethus reach the anodes without changein the 40 quency control field i direction deviating t value of theelectrical or magnetic fields. Thus 40 greater or lesser degree from adirection perpenif 15 peflodically varied instance y uperdicular to theprincipal fi ld By these means the posing an alternating cross fieldcrosswise to the resultant magnetic vector will only be changedprincipa1 fie1d or by tuming the electrode as regards its direction andremains almost in tem relative to the direction of the field lines ofthe principal magnetic field impulse-like curvariable as regards. itsabsolute value. p I

In the accompanying drawings: rent variations Ie are produced, and ifthe work- Figure 1 shows diagrammatically the direcmg point for rest 18Shlfted to and if the variations. of the an le towards ositive or tlonalrelat1onsh1p between two magnetic fields tive Values of a carried 5. i ii applied to a magnetron;

Figs. 2 to 4 inclusive Show was by gg igi g g ggg gg gg 31;; 2313123333,

w c t p p e o my invention are to- Fig. 3- will be obtained. In Fig. 3,there is plained; plotted above the time t as abscissa axis, the Fi 5 n6 w pr f r rran m n s of angle variations da.=ia and at the same'timethe split anodes inamagnetron, and the current impulses Ie areindicated. It can 55 be clearly seen that the emission current varieswith the double frequency of the angle variations. The initial energy ofthe magnetron therefore has twice the frequency as compared with thecontrolling high frequency cross field. In Fig. 4 the impulses Ie areshown in the same relation to t. However it is hereby assumed that theangular variations take place from a rest point Y and Y respectivelyeither in positive values of a only or in negative values andapproximately up to =0. The initial energy of the magnetron in this casehas the same frequency as the controlling auxiliary cross field.

In the preceding discussion only the electron physical actions withinthe discharge tube have been considered. For the exterior design of thecircuit in accordance with the present invention there existsprincipally two difierent possibilities. On the one hand, theoscillatory circuit which can be excited by the current impulses Ie canbe placed directly between anode and cathode as shown in Fig. '7. Thusthe two anodes are connected over the shortest possible distance andwithout interposing a resonant circuit. The characteristics and mode ofoperation of the circuit arrangement shown in Fig. 7 will be set forthmore in detail hereinafter.

A further possibility exists to operate the magnetron to be controlledwith the ordinary symmetrical circuit in which the plate segmentsoscillate towards each other in at least two groups. Without thecontrolling cross field, oscillations would be produced in this circuitby self-excitation and whose frequency would essentially depend upon theinductance L between the groups of anodes, upon the capacity of thepartial anodes and upon an additional capacity C in parallel to theinductance. In adding a high frequency cross field to such aself-excited magnetron, the former acts as a choke valve for the platecurrent in that it permits only such oscillations to assume highamplitudes whose frequency corresponds to the control frequency.

In this method a direct reaction of the controlled oscillations upon thecontrolling oscillation is impossible, since the flying electrons do notperform work at the controlling high frequency of the magnetic field. Byintegrating the product of the force times the distance,-

This is always true, since the force is at a right angle to the path.

H=magnetic vector e=charge of the electron v=ve1ocity of the electron.

This fact will be readily understood, since a magnetic field can onlyproduce a curvature in the path of the electrons but no variation in thevelocity. A magnetic field cannot change the kinetic energy, and neithersupply the electron with work nor can it derive work therefrom.

Arrangements for putting into practice the ments A3 and A4. The opposedanode segments A1 and A3 oscillate in 180 phase relationship. So, also,do the segments A2 and A4. The cross field produced by the conductor Wgand acting upon the electron streams within the cylindrical anodestructure herein shown has been found to provide a very useful controlof the oscillations.

.In Fig. 6, the part of the cross field winding Wg extending parallel tothe longitudinal axis of the anode segments is directly connected withthe anode segments so that in practice these parts of the winding can beomitted. The anode segments are provided at one side with a con-'nection strap B and at the other side with leadin conductors Z forconnecting to the control oscillator.

.Fig. 7 shows a magnetron circuit in which oscillation can be producedonly when a control field is applied. In this embodiment there are buttwo anode segments A1 and A2, which are connected with each other bymeans of a short connection strap B. In the connection for the highfrequency between anodes and cathode K an oscillatory circuit- LC isinserted. This is tuned to a harmonic of the control frequency.The-electrical and magnetic characteristics are so chosen that theoperating point is located at X on the curve Y'Y as shown in Fig. 2. Inthis case anode current impulses of twice the control frequency areproduced and they excite the oscillatory circuit LC.

The parallel connection LC may, if desired, be replaced by a seriesconnection without departing from the spirit of the invention.

Fig. 8 shows a circuit in which the anodes A1 and A3 as well as A2 andA4 of a four part magnetron are joined respectively by two straps B. Thegroups of anodes formed in this way are likewise connected to each otheracross an oscillatory circuit L101 from which the produced highfrequency can be derived. In Fig. 8 the anodes A2 and A4 are connectedto a source of control oscillations M across a Lecher wire line. Thecontrolling source is suitably coupled to-the Lecher system at suchpoints that the voltage with respect to the frequency produced isapproximately equal to zero. The magnetron shown in Fig. 8 is capable assuch of producing oscillations whose frequency is determined by L1C1.This production of oscillations is, so to say, controlled by a separatesource of control. A separately controlled magnetic cross field takescare that the oscillations undergo an amplitudinal increase toappropriate values only when the natural frequency of the circuit L101conforms to the control frequency. The anodes A2 and A4 are identical asregards the oscillations to be controlled and they have thesamepotentialat every instant. As regards the control frequency, the twoanode segmentsare passed bycurrents in the opposite sense. If necessary,the phase conditions between quasi self-excited oscillationsandcontrolling oscillations can be corrected by values acting upon theduration of flow of the electrons. However, this will in general not benecessary, since a fixed phase displacementdoes not cause disturbance.

I claim:

h 1'. A generator of the magnetron type having an electron dischargetube said tube having a plurality of segmented cylindrical anodes and acentrally disposed linear cathode, in combination with means forprodu'cing'a constant magnetic field in the region between the cathodeand anodes, and means including a single conductive loop circuitinterposed between adjacent edges of said segmented anodes forintroducing a magnetic cross field into the same region and at an angleto the lines of force of the constant magnetic field.

2. A generator of the magnetron type having an electron discharge tube,a set of at least four anode segments of cylindrical contour and acentrally disposed linear cathode within said tube, means for producingin said tube a constant magnetic field whose lines of force aresubstantially parallel to the electrode axis of the tube, means forconductively bridging two opposed anodes at corresponding ends thereofthereby to form these anodes into a conductive loop, and means forfeeding high frequency current through said loop from the open endsthereof, thereby to cause said anodes to produce a transversealternating magnetic field perpendicular to the electrode axis of saidtube.

3., A circuit arrangement including a magnetron discharge tube having acentrally disposed linear cathode and a plurality of at least four anodesegments of cylindrical formation co-axially surrounding said cathode,means for producing a constant magnetic field with its lines of forcesubstantially parallel to the electrode axis, a conductive loop havingtwo linear members disposed parallel to said cathode and on oppositesides thereof, and means for producing a magnetic cross field ofalternating polarity in the region of the constant magnetic field, thelast said means being constituted by a source of alternating current fedto said conductive loop.

4. An oscillation generator comprising an electron discharge tube of themagnetron type, said tube having at least four cylindrically segmentedanodes and a centrally disposed linear cathode, means for producing amagnetic field having its lines of force within the discharge zone ofsaid tube substantially co-axial with the cathode and anodes, andfurther means including a circuit disposed between certain of saidanodes and conductive of a high frequency alternating current forproducing an auxiliary magnetic field within said discharge zone at anangle to the axis of said electrodes.

5. A device according to claim 4 and having the means for producing anauxiliary magnetic field inclusive of two of said segmented anodes.

6. A generator of the magnetron type having an electron discharge tube,a plurality of anode segments of cylindrical contour and a centrallydisposed linear cathode within said tube, a conductive loop comprisingtwo parallel members on opposite sides of said cathode and a bridgingmember interconnecting said parallel members at one end thereof, andmeans for feeding high frequency current through said loop from the openends thereof and for producing a transverse alternating magnetic fieldat an angle to the electrode axis of said tube.

KARL FRITZ.

